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MConn Documentation

LTE Interface

LTE

Section titled “LTE”

The MConn Display supports LTE connectivity via an external u-blox cellular module.

Detecting the LTE Module

Section titled “Detecting the LTE Module”

Use the following command to verify that the u-blox cellular module is connected and recognized by the system before initializing LTE networking.

Terminal window
lsusb

Expected output (example):

Terminal window
Bus 001 Device 004: ID 1546:1143 U-Blox AG

Check if LTE Interface is Initialized

Section titled “Check if LTE Interface is Initialized”

Verify wwan0 appears and has a valid IP address before proceeding with LTE traffic. Run the following command:

Terminal window
ip addr

Look for the wwan0 interface and check its content. Expected output (example):

Terminal window
3: wwan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
    link/ether 02:1a:7d:5c:3e:9b brd ff:ff:ff:ff:ff:ff
    inet 10.124.56.23/30 brd 10.124.56.23 scope global wwan0
       valid_lft forever preferred_lft forever
    inet6 fe80::1a7d:5cff:fe3e:9b/64 scope link
       valid_lft forever preferred_lft forever

Initialize LTE Interface

Section titled “Initialize LTE Interface”

If the wwan0 interface is not initialized, then bring up wwan0 with DHCP and confirm the interface is active for network use. Run the following command:

Terminal window
udhcpc -i wwan0

Check if the wwan0 interface is up and has a valid IPv4 address by running the following command:

Terminal window
ip addr show wwan0

Once the wwan0 interface is up, confirm that the LTE connection is fully functional by testing data transfer using a ping request:

Terminal window
ping -I wwan0 8.8.8.8

You should see ICMP replies and low packet loss.

Terminal window
PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: seq=0 ttl=117 time=45.3 ms
64 bytes from 8.8.8.8: seq=1 ttl=117 time=42.8 ms
64 bytes from 8.8.8.8: seq=2 ttl=117 time=44.1 ms
64 bytes from 8.8.8.8: seq=3 ttl=117 time=43.5 ms
Terminal window
--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss
round-trip min/avg/max = 42.8/43.9/45.3 ms

AT Command Interface

Section titled “AT Command Interface”

You can also communicate directly with the LTE modem using AT Commands.

Open Two SSH Terminals

Section titled “Open Two SSH Terminals”

To interact with the modem, you will need two SSH sessions open at the same time:

  • Open two terminal windows side-by-side and SSH into the device in both.
  • One terminal will be used to send commands.
  • The other terminal will be used to read responses from the modem.

Terminal 1 - Send Commands:

Terminal window
echo -e "AT\r" > /dev/ttyACM0

Terminal 2 - Read Responses

Terminal window
cat /dev/ttyACM0

You should see responses such as OK.

Basic Checks

Section titled “Basic Checks”

Run the following AT commands from Terminal 1 and observe the responses in Terminal 2:

  1. AT
  • Verifies communication with the modem.
  • Expected response: OK
  1. AT+CPIN?
  • Checks SIM card status.
  • Expected response: READY
  1. AT+CSQ
  • Displays signal strength.
  • First value indicates signal quality
  • 10–31 = good signal
  • 99 = no signal
  1. AT+CREG?
  • Checks network registration status.
  • 0,1 = Registered (home network)
  • 0,5 = Registered (roaming)
  • 0,0 = Not registered

APN Configuration

Section titled “APN Configuration”

Set the APN required by your SIM provider:

AT+CGDCONT=1,"IP","<your_apn>"

Example:

AT+CGDCONT=1,"IP","spoke-zone.com.attz"

Attach to Network

Section titled “Attach to Network”

Attach the modem to the packet data network:

AT+CGATT=1

Verify attachment:

AT+CGATT?

The expected response is 1.

Production Configuration

Section titled “Production Configuration”

The LTE module is configured during production with the following commands:

AT+UUSBCONF=2
AT+CPWROFF
  • AT+UUSBCONF=2 enables USB networking mode
  • AT+CPWROFF powers off the modem so the configuration is applied on the next boot